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Commit 7fc80b7b authored by Krzysztof Helt's avatar Krzysztof Helt Committed by Linus Torvalds
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neofb: simplify clock calculation 



There is nothing to gain by converting value in kHz to fixed point MHz.
Just calculate everything in kHz.

A reorder of the loop allows reducing number of iterations (check if
frequency is not too high already).

Signed-off-by: default avatarKrzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5798712d

drivers/video/neofb.c

+14 −18
Original line number Diff line number Diff line
@@ -201,7 +201,6 @@ static int neoFindMode(int xres, int yres, int depth) 
 *

 * Determine the closest clock frequency to the one requested.

 */

#define REF_FREQ 0xe517		/* 14.31818 in 20.12 fixed point */

#define MAX_N 127

#define MAX_D 31

#define MAX_F 1
@@ -211,27 +210,24 @@ static void neoCalcVCLK(const struct fb_info *info, 
{

	int n, d, f;

	int n_best = 0, d_best = 0, f_best = 0;

	long f_best_diff = (0x7ffff << 12);	/* 20.12 */

	long f_target = (freq << 12) / 1000;	/* 20.12 */

	long f_best_diff = 0x7ffff;



	for (f = 0; f <= MAX_F; f++)

		for (n = 0; n <= MAX_N; n++)

			for (d = 0; d <= MAX_D; d++) {

				long f_out;	/* 20.12 */

				long f_diff;	/* 20.12 */



				f_out =

				    ((((n + 1) << 12) / ((d +

							  1) *

							 (1 << f))) >> 12)

				    * REF_FREQ;

				f_diff = abs(f_out - f_target);

				if (f_diff < f_best_diff) {

		for (d = 0; d <= MAX_D; d++)

			for (n = 0; n <= MAX_N; n++) {

				long f_out;

				long f_diff;



				f_out = ((14318 * (n + 1)) / (d + 1)) >> f;

				f_diff = abs(f_out - freq);

				if (f_diff <= f_best_diff) {

					f_best_diff = f_diff;

					n_best = n;

					d_best = d;

					f_best = f;

				}

				if (f_out > freq)

					break;

			}



	if (info->fix.accel == FB_ACCEL_NEOMAGIC_NM2200 ||
@@ -248,11 +244,11 @@ static void neoCalcVCLK(const struct fb_info *info, 
	par->VCLK3Denominator = d_best;



#ifdef NEOFB_DEBUG

	printk("neoVCLK: f:%d NumLow=%d NumHi=%d Den=%d Df=%d\n",

	       f_target >> 12,

	printk(KERN_DEBUG "neoVCLK: f:%ld NumLow=%d NumHi=%d Den=%d Df=%ld\n",

	       freq,

	       par->VCLK3NumeratorLow,

	       par->VCLK3NumeratorHigh,

	       par->VCLK3Denominator, f_best_diff >> 12);

	       par->VCLK3Denominator, f_best_diff);

#endif

}